Hydrogen Horizons: Renewable and Non-Renewable Energy Synergies for a Greener Environment

Abstract

The global energy crisis, together with rising greenhouse gas emissions, has intensified the search for clean, sustainable energy carriers. Hydrogen has emerged as a promising solution to decarbonise high emission industrial sectors and facilitate the integration of intermittent renewable energy sources into the grid. This review provides a systematic and comparative analysis of current and emerging hydrogen production methods, categorising them by energy source (renewable and non-renewable) and by technological pathway, including steam methane reforming (SMR), water electrolysis, biomass gasification, coal gasification, and thermochemical water splitting. From observations, while fossil fuel-based methods (primarily SMR) currently dominate global hydrogen supply due to lower production costs (0.9–3.2/kg H₂) and technological maturity, they are inherently carbon intensive, emitting ≈9 kg CO₂ per kg H₂ without carbon capture. On the other hand, renewable based routes, particularly electrolysis powered by solar and wind, offer near zero emission potential but face persistent challenges related to high capital costs, intermittent energy supply, and lower technology readiness levels. The review evaluates the trade-offs and scalability challenges of various hydrogen production methods, emphasizing the importance of novel materials for improving catalyst durability and electrolyzer efficiency. It also covers hydrogen purification techniques required for fuel cell standards. The analysis concludes that a combination of blue (fossil with carbon capture) and green (renewable) hydrogen is necessary, tailored to regional resources and infrastructure. The review also outlines key future research directions, including the advancement of methane pyrolysis, plasma reforming, process optimization, and the development of robust storage materials.